The non-prepublished German Patent Application No. DE 43 38 342 describes a method and a device for forming a simulated signal relating to the temperature of the exhaust gas of the exhaust gas sensor, or of the catalytic converter. In the known method, there is provision for a steady state exhaust gas temperature to be determined with a characteristic curve. Using a first filter, the variation over time of the exhaust gas temperature upstream of the catalytic converter is simulated on the basis of the steady state exhaust gas temperature. Using a second filter, the temperature of the catalytic converter also can be determined.